Digital audio and video signals offer many advantages over conventional media in terms of audio quality and ease of transmission. With the ever-increasing popularity of the Internet, digital content—such as a multimedia clip—has become a mainstay ingredient of the Web experience, buoyed by such advances as the increasing speed at which data is carried over the Internet and improvements in Internet multimedia technology for playing such multimedia clips. Every day, numerous digital content files are added to Web sites around the world.
As used herein, digital content and digital content file indicate a digital file or a digital signal (or bit stream), in whole or part, which embodies multimedia content, including audio, video, images and text. A digital content file may be stored and retrieved, transmitted and received, or the like. The following discussion will refer to one or more digital content files, although it should be understood that reference to a digital content file is a reference to any digital content that may be stored in memory and/or transmitted from a first party to a second party.
The transmission and “sharing” of digital content files has become increasingly more efficient, so have illegal acts of piracy, i.e., illegal sharing, involving digital content files. For example, an imposter may download a digital content file from the Internet, claim the work for his own, and sell the work to unsuspecting consumers. In such an instance, the true owner of the work represented in the digital content file loses out on monetary gain as well as proper recognition as the creator of the content. Additionally, the consumer is denied the security of obtaining authentic multimedia content from the true owner or creator of the content. Furthermore, the true owner of the work contained in the digital content file loses control over how the work is used, e.g., limited/unlimited playing, copying, etc. In many cases, imposters attempt to dupe devices rather than people. For example, an imposter's goal may be to create a counterfeit digital content file that will play on a “good machine,” i.e., a device that is designed to play only authentic content.
One way that has been utilized to protect an owner of digital content from piracy is known as “watermarking” or digital watermarking. A digital watermark is a digital sequence that is embedded into digital content but is imperceptible when the content is played. The watermark is virtually unremovable from the content, meaning that if the watermark is removed, the perceptual quality of the digital content is significantly altered.
The main application of digital watermarking is the protection of intellectual property rights. Watermarking allows for embedding a copyright label into the content that can identify the true copyright owner and, in some cases, identify permissible uses of the content. In the example given above, if the digital content file that is downloaded from the Internet contains a digital watermark, then the pirate cannot claim the work as his own unless there is a way for the pirate to remove the watermark before claiming the work as his own. However, watermarks are designed so that they are virtually impossible to remove.
A problem with traditional watermarking techniques is that it is a difficult task to create and embed a watermark that can be reliably protected and that cannot be easily removed. Increasing the amount of information contained in a watermark means increasing the size of the watermark. Increasing the size of the watermark means increasing the difficulty of embedding the watermark in digital content so that it is difficult to remove without destroying the content.
Current SDMI (Secure Digital Music Initiative) standards dictate that a watermark signal should have a length of seventy-two (72) bits. This finite number of bits necessarily limits the amount of information contained in the watermark signal. Therefore, a copyright owner does not have a great amount of flexibility to dictate permissible use of the digital content.
FIG. 1 is a schematic block diagram of a prior art watermarking system 100. A pseudo-random number generator 104 generates a key 106 that is used by a watermark generator 108 to produce a watermark 110. A modulator 112 incorporates an ID (identification) tag 114 into the watermark 110. An embedder 116 incorporates the watermark 110 into a digital content file 118 to produced marked content 120.
The system 100 includes a content player 122 that includes a watermark detector 124 that is designed to look for an embedded watermark in a digital content file. The content player 122 includes a copy of the key 106′ that was used to create the watermark 110. The watermark detector 124 uses the key 106′ to determine if the marked content 120 contains the watermark 110′.
If the watermark 110′ is detected in the marked content 120, a demodulator 126 processes the watermark 110′ to determine the ID tag 114′ and, hence, the copyright owner. The ID tag 114′ is utilized to locate a rules document 128 that identifies legitimate uses of the marked content 120. If the content player 122 is authorized by the rules document 128 to play/copy the marked content 120, then the marked content 120 is played and/or copied by the content player 122. If the watermark detector 124 does not detect the watermark 110′ in content (not shown) input to the content player 122, then the content player 122 either allows unlimited use of the content or it does not process the unmarked content.
The previous example of a prior art watermark detection system is given for exemplary purposes only. It is noted that the description is not intended to identify a single system or an exclusive method of generating, embedding and/or detecting a watermark in digital content. Rather, the description of the exemplary system is intended to provide a general background for the detailed description of the invention(s) that follow. Those skilled in the art will understand that the described watermark detection system may be implemented in numerous ways with numerous variations to the described system.